Source : Webster's Revised Unabridged Dictionary (1913)

Superstitious \Su`per*sti"tious\, a. [F. superstitieux, L.
   superstitiosus.]
   1. Of or pertaining to superstition; proceeding from, or
      manifesting, superstition; as, superstitious rites;
      superstitious observances.

   2. Evincing superstition; overscrupulous and rigid in
      religious observances; addicted to superstition; full of
      idle fancies and scruples in regard to religion.

            Ye men of Athens, I perceive that in all things ye
            are too superstitious.                --Acts xvii.
                                                  22.

   3. Overexact; scrupulous beyond need.

   {Superstitious use} (Law), the use of a gift or bequest, as
      of land, etc., for the maintenance of the rites of a
      religion not tolerated by the law. [Eng.] --Mozley & W. --
      {Su`per*sti"tious*ly}, adv. -- {Su`per*sti"tious*ness}, n.

Source : WordNet®

superstitiously
     adv : in a superstitious manner; "superstitiously he refused to
           travel on Friday the 13th"